This invention relates to an image processing apparatus, and more specifically, an image processing apparatus for correcting the inclination (rotating correction) of an original image read slantwise.
In a digital copying machine disclosed in the Japanese patent laid-open publication No. 4-148279, an original set slantingly on an original setting plate of the image scanner is processed by the following inclination correcting First, coordinates of four vertexes of the original are detected by the pre-scan. In accordance with those coordinates, the inclined angle of the original is detected. At the scanning for reading the original image (hereinafter called a xe2x80x9cregular scanxe2x80x9d), the read image data are stored by a line-buffer for a plural number of lines. The process of reading the image data from the line-buffer is performed in accordance with the address corrected by the inclined angle detected as above.
In the Japanese patent laid-open publication No. 5-252379, the other inclination correcting is disclosed.
While reading the original image, the inclined angle is detected at real time in accordance with the difference between a main-scanning original-edge position on the preceding line and that on the current line. And by using the inclined angle, the image shifting is performed in the main-scanning direction and the sub-scanning direction respectively. The image shifting in the sub-scanning direction is arranged to be performed by correcting the writing address in the image memory (the page memory).
The constitution disclosed in the Japanese patent laid-open publication No. 4-148279 is superior in respect of not using the page memory. According to the constitution, however, because the rotating based on the affine transformation is processed by using the reading address control at the time of reading in a buffer memory, the address generating circuit becomes complicated. And considering the case that the address calculated result is not an integer, it is necessary to perform the interpolating and so on.
In the constitution disclosed in the Japanese patent laid-open publication No. 5-252379, because the image shifting in the sub-scanning direction is performed at the time of the writing into the image memory, it is required to generate the non-sequential writing address. In a result, the address generating circuit becomes complicated. And since the magnification difference generated at the inclination correcting is not considered in such constitution, the magnification of the image after the inclination correcting is different from the original size.
The present invention is proposed in order to solve the above-mentioned problems, and has an object to provide an image processing apparatus able to correct the inclination and the magnification difference generated at the rotating correction by means of adding the simple constitution of shifting an image data only in the main-scanning direction to the conventional image processing apparatus.
In order to achieve the above object the invention adopts the following means. As shown in FIG. 14(a), the invention is presumed to be an image processing apparatus for correcting the inclination of image data while reading originals as image data by the electric scanning
Inclined angle detecting means 66 detects the inclined angle of the original. First line shifting means 65 shifts the image data in the main-scanning direction by specific number of lines in the shifting amount corresponding to the inclined angle detected by the inclined angle detecting means 66. First image memory 88 stores the image data shifted by the first line shifting means 65. First rotating means 85 rotates the image data stored in the first image memory 88 by 90 degree or 270 degree, so that the main-scanning direction of the initial image data could change to the sub-scanning direction. Namely, the main-scanning direction is interchanged to the sub-scanning direction. Second line shifting means 91 shifts the image data rotated by the first rotating means 85 in the main-scanning direction (in the sub-scanning direction of the initial image data) by specific number of lines in the shifting amount corresponding to the inclined angle detected by the inclined angle detecting means 66. According to such arrangement of adding the simple constitution of shifting an image data only in the main-scanning direction to the conventional image processing apparatus, it is possible to correct the inclination of an initial image data not only in the main-scanning direction but also in the sub-scanning direction by rotating the initial image data.
In the invention, the image data to be shifted by the first line-shifting means 65 is an image signal transferred at the fixed rate. The first line shifting means 65 advances or delays the timing the signal determining the effective length of the image signal becomes enabled along with the progress of the sub-scan, thereby the image data is shifted as described above. According to this arrangement, as a part of the inclination correcting (that is, the shifting by the first line shifting means 65) is performed along with reading the image data (at a step of the image signal), it is possible to shorten the time for the inclination correcting.
And the magnification correcting means which are not shown corrects at the time of reading the image data the magnification difference which is generated by the inclination correcting based on the inclined angled detected by the inclined angle detecting means 66. As described, when the magnification correcting is performed at the time of reading the image data, the magnification correcting is executed for the multi-valued image data. Therefore it is possible to keep the deterioration of the picture quality to a minimum.
In case the first line shifting means 65 is common to the second line shifting means 91, the constitution of the hardware can be more simplified. Namely, in case of including a selector for selecting either an image data at the time of reading or an image data rotated by the first rotating means 85 and inputting it into the first line shifting means 65, it is possible to obtain the same effect as described above without using the second line shifting means 91.